I. Field of the Invention
The present invention relates generally to train handling equipment, more particularly, to railway car spotting or indexing systems used to position cars in a trip precisely along a track to be addressed by loading and unloading operations at fixed stations. One type of system of the class commonly employs alternating left and right indexing devices, each of which includes a carriage having a pair of opposed pivotally retractable ruggedly constructed car-engaging pusher devices known as xe2x80x9cdogsxe2x80x9d which push against the bogey carriage frames or axles of the car. In addition to being used as pushers, the dogs are normally employed in detecting the presence of a car by advancing the indexer with the dogs up until a dog is deflected by a bogey frame or axle. This invention focuses on providing improvements in the operation of a bogey frame pushing system by eliminating the need to use the dogs, themselves, to detect the presence of a car and providing a system that allows separate control for each dog in a reversing dog carriage assembly associated with a car-spotting setup.
II. Related Art
Freight-hauling railway cars need to be positioned proximate freight or cargo handling equipment during loading and unloading operations. Freight, in the form of bulk cargo such as grain, coal, iron ore or the like, is typically dumped or emptied out of railway cars by dumping the cars themselves or by using stationary freight-handling equipment such as chutes and conveyor equipment located in pits beneath the tracks. Coal gondolas and cars for transporting grain or other finely divided dry bulk agricultural material may be covered and provided with a plurality of spaced bottom discharged hopper bins or chutes accessing the main storage volume enclosed by discharge gates. As discussed below, these gates may be operated more easily by using tripper rods which extend outward from the sides of the cars to allow easy access and gate operation. These cars are also designed to be positioned for discharge over dedicated recessed receiving facilities situated at fixed stations such as grain or coal bins and conveyors which are positioned beneath the railroad track.
In the discharge operation, a locomotive roughly positions one end of a string or trip of cars to be unloaded over the receptacle. Locomotives, of course, are not well suited for indexing or precisely positioning individual cars or even sets of cars along the track, let alone over individual cargo receiving bins. To this end, positioning devices known as railway car spotters, indexers or positioners have been built and operated at fixed stations.
Railway car indexers of interest here include at least one car-engaging dog for engaging at least one railway car in a string or trip of cars and moving the string a given distance along the railroad track. The engaging member is often situated and operated along an auxiliary indexer track or guideway juxtaposed in a parallel relation to the railroad track itself in the fixed receiving facility. Fluid-operated linear actuators, such as hydraulic cylinders may be connected to chains, or chains and sprockets driven by hydraulic or electric motors may be used to supply power for moving the dogs and hence, the railway cars.
In one type of indexing apparatus, dogs in the form of heavy vertically pivoting car-engaging arm members are used which are designed to engage either the railway bogey wheel truck frame or an axle. The dogs are smaller than car coupler engaging arms and are carried on dog carriages situated either between the rails of the track to engage the axle or next to the track to engage the bogey truck frame. Bogey frame-engaging dog systems may be further divided into two types. One type that includes xe2x80x9clow dogsxe2x80x9d which are dogs that engage the lower portion of the truck frame below axle height; the other employs xe2x80x9chigh dogsxe2x80x9d which engage the frame at or above the height of the axles. One such system using high dogs is described in U.S. Pat. No. 5,709,153 to Brandt, the inventor of the present invention, and is assigned to the same assignee as the present invention.
These car moving systems typically include left and right indexers which, in effect, operate alternately to hand off consecutive sequentially connected cars in a trip of cars so that the entire trip may be advanced and unloaded, one car at a time. Each indexer is designed with the ability to stop at any point during an alternating stroke. Traditionally, indexer carriages have been hydraulically operated and designed to travel forward with spaced oppositely directed dogs which, in the case of bi-directional or reversing systems, are pivotally mounted (bottom pivoted) to drop toward each other and are raised facing each other to sense and engage a railcar. In this manner the back side of a dog will initially strike an interfering object enabling the struck dog to pivot or deflect downward away from the object. The event of a dog contacting the bogey frame can be sensed by a resulting change in system hydraulic pressure produced by the deflection of the dog. This has become a trusted and reliable method for sensing the presence of and then engaging a car. Using this method, the first dog encountering the bogey frame of a car is pushed down from behind and the second dog in the pushing posture engages the bogey frame of the car as the indexer continues to move. While these systems work quite well with conventional cars, tripper rods which have since been added to the outside of many types of railcars have introduced a problem. These devices extend outward from the lower portion of the side of the railcars and are used as a convenient method for one standing along side of the car to operate the bottom discharge mechanisms in gondolas, hopper and other bottom discharged cars. These devices are not compatible with bogey carriage engaging dogs, however, because the rods are positioned such that they can be struck and damaged or destroyed by a raised dog further possibly resulting in catastrophic damage to the railcar hopper opening mechanism.
Devices utilizing sprockets and continuous chains have been devised which can be used to lower both dogs of an indexer or carriage simultaneously during the car finding or engaging operation to prevent interference with car tripper rods. These devices, however, do not allow operation with a single raised dog in contact with the bogey frame once sensed and operating as a pusher dog.
Accordingly, there exists a definite need to provide a mechanism to sense cars that does not require contact with the dogs thereby eliminating the possibility of tripper rod damage.
Accordingly, it is a principle object of the present invention to provide an improved car spotting system having dogs which operate on the bogey carriage when moving the cars but which do not interfere with the existence of any tripper rods or other protruding devices on the cars.
It is a further object of the present invention to provide an indexing system that does not use the dog devices to sense the presence and location of a railway car.
Another object of the invention is to provide such an indexing system in which the forward and rearward dogs of each carriage on the left and right indexers are individually controllable.
Other objects and advantages of the invention will become apparent to those skilled in the art upon familiarization with the specification, drawings and claims contained herein.
The present invention provides a railway car indexing or spotting system capable of detecting bogey frames in the presence of interfering devices such as tripper rods. The system is useful for both high or low dog indexers, whether una-directional or reversing. The system features independent bogey frame detection devices that do not require direct contact between the dogs and the bogey frame to detect the presence of a railcar. This eliminates the need for the indexers to travel forward with dogs raised to engage a railcar. Such sensing devices may include limit switch devices or roller cam devices connected to the hydraulic system which do not interfere with other aspects or appendages of the railcar.
Independent pivotal operation is enabled for each dog in the spotting system. With dual or reversing systems, independent control is provided for both dogs in each of the left and right index carriages and for each dog in single dog non-reversing index pairs.
The dual dog reversing indexing carriages each include a pair of opposed pivotally mounted dogs, which can be high or low, and which can be used to move cars of a trip in either direction in conjunction with a second indexing carriage which operates in tandem with the first to hand off each car and continue the motion of the trip. The control of individual dogs of an indexer in such a system is an important aspect of the invention. As described in the detailed description, each dog is a bottom pivoted pusher arm which is spring biased to remain in a raised posture unless forced down by a bogey carriage, by the control system of the invention or other means to overcome the spring bias. Each dog then is designed to pivot in one direction and engage and pull in the other. The individual dog control system of the invention includes a fluid operated linear actuator, preferably a hydraulic cylinder, which tensions a chain extending between a fixed chain connector and the rod of a fixed cylinder, passing over idler sprockets therebetween which control the posture of the dog. A control system for each carriage includes a pressure compensated hydraulic pump or other source which supplies high pressure fluid for the operation of both dogs. Each dog has its own pressure reducing and directional control valves so that the tension on the individual chains associated with each dog can be separately adjusted. In this manner, at least the reduced pressure is applied to the hydraulic cylinders any time the power to the unit is on. The pressure as limited by the pressure reducing valves or the high pressure fluid are selectable using an in-line controlled two-position valve. The pressure reducing valves are set at a pressure that is sufficient to keep each chain taut and on the sprockets, but insufficient to lower the dogs.
In operating a high dog system using the invention, when the indexer is moving through the track looking for a car, or performing a transfer, the dogs will be pulled down by retracting the cylinders at higher pressure, perhaps 1600 psi. When the dogs are down, another locating system, such as a cam actuated system, will become active to look for the next bogey truck frame of a railway car. In the case of a cam operated system, spaced deflectable cams, one near each high dog, are connected in the system in a manner such that when a cam goes under a bogey frame of the car, it will deflect and the chain of the corresponding dog will be pulled causing a pressure spike that is used to indicate that the indexer has gone under a bogey frame of a car. The pressure spike will go away when the cam actuator comes out from under the bogey frame and the cam returns to a neutral position. The indexer will stop moving to allow the appropriate dog, i.e., the dog that engages in the direction the cars are being moved, to assume a raised position and the indexer will move it towards the car. In this manner, a bogey frame can be engaged as a transfer from the opposite indexer or as an initial engagement of the trip of cars without initially raising the dogs.
In the case of a low-dog indexing system of the dual dog or reversing class, in many cases the dogs themselves can still be used to sense the presence of the bogey frame in the traditional manner if there is no danger of damage to the cars or the system can be operated in the manner of a high-dog system using separate limit switches operated by movement of the cylinder rod chain connector linking devices to find the next bogey wheel frame. If the system is operated in the traditional manner, the pressure is limited by the pressure reducing valves to an amount adequate to keep the chain taunt, but inadequate to lower the dogs. In this manner, when a dog is lowered by engaging a bogey frame, this causes the chain tension to decrease and the cylinder to retract a given amount. This deactivates a limit switch, normally activated by the chain connector as the connector moves away from it. This action signals the PLC to let it know that the carriage has traveled under a railcar. As the carriage continues to reverse, the dog will rise and the sensor will be reactivated, thereby completing a new engagement or transfer.